This is the reason I had my camera on hand to take pictures of the truck actually, lol.
My big "steam-powered airship" all made out of legos, my 3d medium of choice. I've had them since I was really young, and I kept them at my dad's when I moved.. So when I stay over there for a while, I usually work on something.. Airships being my favorite, as they are more fun to build than to draw.

For nerds interested in what it would be like in real life, or if it was say.. like one in an anime or game (EG: the last exile, skies of arcadia, Steam Boy)
It's powered by a pair of large steam engines, that run the main propellers, as well as numerous maneuvering fans and lift fans. Though it's kept aloft by gas tanks dispersed throughout it's hull. (Most likely hydrogen)
The lower deck carries 6 turrets mounting 2 light cannons each, all built on sliding carriages, and when the firing ports are open, can be moved up for a wider firing arc. It's main turret mounts two heavy battleship cannons, and it also has a turret on each side, and one in the back that mount a single heavy cannon. There are also two exposed light turrets like those on the gun deck, but on exterior platforms.
There are also several small machine gun turrets placed around it, for small aircraft defense, and two counter-missile launchers for shooting down large warheads.

If I work it into a story I'll go into detail about it, and draw some pics.. (This would be in the Aven world setting)